On Wed, Aug 09, 2017 at 05:31:08PM -0400, A. Maitland Bottoms wrote: > Let me just mention in this thread the volk package. Vector Optimized > Library of Kernels implements a high level set of DSP operations, with > fast implementations chosen at runtime depending on available CPU SIMD > instructions. > > There is always a generic fallback implementation that runs on any CPU. > > So a tool looking for special instructions will certainly find them in > volk.
Yeah, that's why the high number of false positives. I expect the vast majority of ISA extension users to implement such a fallback. There are, though, some quite prominent exceptions like chromium-browser on i386 (sse2) or rustc compiled software (new versions of firefox) on armhf (neon) that have a hard dependency. Thus, it'd be nice to have a way to automatically detect such cases, but I don't know of a anything better than testing manually. Which is extra unfun as any pre-sse2 (or pre-sse3) machine is crummy to the extreme, making unaccelerated qemu significantly faster than real silicon. And neither is fast enough to not make such testing a pain in the posterior. Meow! -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢰⠒⠀⣿⡁ James Damore is a hero. Even mild criticism of bigots these days ⢿⡄⠘⠷⠚⠋⠀ comes at great personal risk. ⠈⠳⣄⠀⠀⠀⠀